Method and apparatus for welding with a trigger hold

ABSTRACT

A method and apparatus for welding is disclosed. The method includes sensing the status of a trigger between an on position and an off position. A system latch is set or released based on the trigger status and the latch status. The system latches on when the trigger is held for a predetermined time (and the latch was previously off). The latch is released when the trigger is pulled and released when the latch was previously on. When the latch is off, pulling the trigger turns the system on, and releasing the trigger before the predetermined time turns the system off. The latch may also be released when welding current drops below a threshold. The time might not start until after welding current is flowing. A welding wire feed speed control potentiometer on a torch is also disclosed. The range of the torch potentiometer is from a minimum to a value dependent on the control panel welding wire feed speed. A run-in wire feed speed control is also disclosed. The range of the run-in wire feed speed is from a minimum to a value dependent on the control panel or torch welding wire feed speed.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the art of weldingpower supplies. More specifically, it relates to controlling weldingpower supplies having a wire feeder and controller.

BACKGROUND OF THE INVENTION

[0002] Many welding applications such as MIG (metal inert gas) or GMAW(gas metal arc welding) utilize a welding power supply (system) with awire feeder to provide filler metal to the weld. A welding-power supplyor system as used herein includes one or more of the followingcomponents: a wire feeder, a power source or source of power, a torch orgun, a wire feeder controller, and a power source controller to controlthe various components (it may also exclude some of these components,such as the power source). The components may be packaged discreetly, orin various combinations. Additionally, the wire feeder controller may bepart of, distinct from but cooperates with, or independent of the powersource controller.

[0003] One prior art welding power supply/wire feeder system includes aMiller XRA or XRW® wire feeder used in combination with a Miller DeltaWeld® power source. This system has the control panel, including userselectable devices, on the front or control panel of the wire feeder.

[0004] Generally, the wire feeder motor will provide wire at a nominallyconstant speed (typically given in inches per minute) in response to thewire feed speed controller. The power source welding output is likewiseresponsive to the welding power source controller. The controllers haveuser selectable devices to allow the user to set parameters such as weldwire feed speed, weld current, weld voltage, and run-in wire feed speed.The input devices are typically potentiometers mounted on the controlpanel of the system or wire feeder, but may include other userselectable input devices, including digital devices. The user sets theparameters, and then pulls a trigger on a torch to begin welding. Thetrigger activates the wire feeder, causing it to field wire. The triggeralso activates the source of power, causing it to provide output power(often by closing a relay or contactor).

[0005] Wire feed welding power supplies are used for a variety ofprocesses, including spot or tack welding, and continuous welding. Someapplications use both processes. For example, when assembling a truckframe or other large object, the welder will often spot weld around theedge of the frame to tack the frame together, and then fill in with acontinuous weld. Welding power supplies often come with many feet (30,50 or 100 or more) of welding cable to accommodate welding various sidesof such large objects. The power supply or system can then be left onone side of the object to be welded, and the welder can pass the torchcable around or underneath, and weld the opposite side without movingthe power supply or system.

[0006] Tack welding is performed by periodic activation of the source ofpower and wire feeder, to weld in a specific location. Activation istypically accomplished by pulling a trigger on the torch. The trigger isreleased when the spot or tack weld is completed, and the source ofpower shuts down and wire feeder stops.

[0007] Continuous welding is accomplished by pulling the trigger, andthe power source provides power and/or the wire feeder feeds wire, solong as the trigger remains pulled. Some prior art systems included atrigger hold or latch feature. With this feature, pulling the triggerlatches the power supply or system on until the trigger is retriggered.

[0008] There are a variety of prior art trigger bold implementations.One is a simple design which automatically latches or unlatches eachtime it is pulled. This type of prior art system typically uses analternating relay, or its electronic equivalent, and the circuit merelyprovides that the first trigger closure initiates the welding operation,and the second trigger closure will terminate it. One disadvantage ofthis type of system is that the operator could walk away from the systembefore terminated welding operation, and the system would continue tooperate. Similarly, an inadvertent triggering, such as a person bumpingthe trigger, could also cause the system to be initiated. This may bedangerous and will likely cause an undesirable amount of wire to be fedbefore shutting down by retriggering.

[0009] Another type of trigger hold system relies on a current sensingrelay to latch the system in operation. However, this requires that thearc be terminated in order to stop the wire feeding, which often resultsin too much wire being drawn from the tip of the torch when the operatorpulls the torch away from the workpiece to extinguish the arc.

[0010] The Miller 50M Intellmatic® wire feeder had a nonstandard optionthat included a trigger latch which was set by pulling the trigger, andthen releasing the trigger prior to the expiration of period of time. Ifthe trigger was not released within the period of time then the latchwas not set, and continuous welding was performed manually.

[0011] A trigger hold system described in U.S. Pat. No. 4,531,045combines the three previously described systems by requiring the welderto pull a trigger, hold the trigger pulled until current flow wasestablished, and then within one second of the initiation of currentflowing, release the trigger to set the latch. The latch is removed byre-triggering. After a two second delay the system may be turned onagain by another trigger.

[0012] These prior art trigger hold schemes are designed for onlycontinuous welding, and each does not work well for spot wieldingapplications. Each will cause the latch to be set when Lack welding(because the time to weld the tack will likely be less than thethreshold). Thus, to stop the tack weld the trigger would have to beretriggered, often resulting in excess wire feeding for the tack weld.

[0013] Some prior art systems attempted to overcome this disadvantage byproviding a toggle switch on the control panel that allowed the user toselect between the trigger hold mode, and a non-hold mode (useful forspot welding) unfortunately, for applications where the welder is somedistance from the control panel (such as welding on a truck frame or theopposite side of another large object) it is not convenient for thewelder to switch between spot or tack welding and continuous welding.

[0014] Accordingly, a trigger hold that is useful for both continuousand tack or spot welding is desirable. Such a trigger hold willpreferably be operable by the user, at the torch, and will cause thesystem to latch on for continuous welding, but will not cause the systemto latch on when tack or spot welding.

[0015] Some prior art welding power supply/wire feeder systems allow theuser to set to the wire feed speed at the torch. This allowed the userto adjust the wire feed speed, without returning to the control panel.Typically, the torch controller was a pot that allowed the user toselect the full range of speeds. One disadvantage of this type of torchcontrol is that the relatively small knob on the torch was used tocontrol the full range of speeds, and it was difficult for the user to“dial in” the desired speed. Accordingly, a welding wire feed speedcontrol located on the torch, that allows the user to more accuratelyselect the speed is desirable.

[0016] Prior art welding power supplies/wire feeders also sometimesinclude a feature called run-in. Run-in allows the welder to control thespeed at which the wire approaches the workpiece prior to the arcforming and welding starting. Prior art controllers allow the welder toselect the run-in speed at any speed over the entire range of wire feedspeeds. This, however, is dis-advantageous because it may be difficultto select the proper run-in speed, relative to the wire feed speedduring welding. Accordingly, a run-in control that allows the welder toselect the wire feed speed during run-in, relative to the wire feedspeed during welding is desirable.

SUMMARY OF THE PRESENT INVENTION

[0017] According to a first aspect of the invention a method ofproviding welding power includes sensing the status of a trigger betweenan on position and an off position. If the trigger is moved to the onposition, and wire is not being fed, then one or both of providing powerto the weld and feeding wire is initiated. If the trigger is moved fromthe on position to the off position within a predetermined period oftime after the trigger was moved to the on position then no more poweris provided, and/or no more wire is fed. If the trigger is moved fromthe on position to the off position after the predetermined period oftime after the trigger was moved to the on position, then the system islatched on by continuing to provide power to the weld and/or continuingfeeding wire even when the trigger is released. If the trigger isretriggered, the latch-condition is ended by stopping the providing ofpower to the weld and/or stopping the feeding of wire.

[0018] According to one alternative power is controlled on and off byclosing and opening a power contactor.

[0019] According to another alternative the latch condition is left whenwelding current drops below a threshold, and/or the latch condition isentered after the predetermined period of time has past and when weldingcurrent is flowing.

[0020] The predetermined period of time is user adjustable according toanother alternative.

[0021] A second aspect of the invention is a welding system including asource of power and a controller. The controller includes a triggerinput that indicates whether a trigger is on or off, and has a wirefeeder control output and/or a power control output. A trigger oncircuit responds to the trigger moving to the on position, and activatesthe system. A trigger off circuit responds to the trigger moving fromthe on position to the off position within a predetermined period oftime after the trigger was moved to the on position. A latch on circuitresponds to the trigger moving from the on position to the off positionafter a predetermined period of time after the trigger was moved to theon position. A latch off circuit responds to the latch on output and thetrigger moving from the off position to the on position, or from the offposition to the on position and back to the off position.

[0022] According to another alternative at least two of the latch oncircuit, latch off circuit, trigger on circuit, and trigger off circuitform a single circuit.

[0023] According to another alternative a welding power supply or systemcontrol panel is connected to the controller. A first user selectableinput device is located on the control panel. The first device providesa first user selected setting provided to the controller. A second userselectable input device is located remotely from the control panel, andselects a second user selected setting between a predetermined value anda value responsive to the first user selected setting. The second userselectable input device is located on a welding torch, and relates towire feed speed in various alternatives.

[0024] According to another alternative a user selected run-in settingconnected to the controller. It has a range from a minimum to a maximum,and the maximum is dependent on the second user selected setting, andthe maximum is the second user selected setting in various embodiments.

[0025] Other principal features and advantages of the invention willbecome apparent to those skilled in the art upon review of the followingdrawings, the detailed description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a block diagram of the preferred embodiment of thepresent invention;

[0027]FIG. 2 is a flow chart illustrating one aspect of the preferredembodiment of the present invention;

[0028]FIG. 3 is a circuit diagram implementing one aspect of thepreferred embodiment of the present invention; and

[0029]FIG. 4 is a circuit diagram implementing an aspect of thepreferred embodiment of the present invention.

[0030] Before explaining at least one embodiment of the invention indetail it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments or of beingpracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] While the present invention will be illustrated with reference toparticular components, embodiments, circuit diagrams and flow charts, itshould be understood at the outset that the invention can also beemployed with other components, embodiments, circuits, programs, etc.

[0032] The invention generally relates to welding systems having powersources used with wire feeders, and controlling the feeding of the wireto the workpiece. The invention is easily understood with respect toprior welding power supplies, such as the Miller XRW or XRA® wirefeeders, used with, for example, a Miller Delta Weld® power source.

[0033] The invention provides that the latch or trigger hold is providedwhen the welder pulls the trigger, and keeps it pulled for more than apredetermined time. The predetermined time may be user adjustable, forexample by a potentiometer on the control panel. This allows the user tospot or tack weld and continuous weld by controlling the time thetrigger is pulled. Spot welding is performed by pulling the trigger fora brief period of time (less than the predetermined time), and when thetrigger is released the latch is not set, and thus the wire feeder willstop feeding wire and the source of power will stop providing power.However, for continuous welding the trigger latch is set when the userholds the trigger pulled for more than the predetermined time.

[0034] Additionally, the controller of the present invention providesthat the user may set the wire feed speed at either the control panel orat the torch. (As used herein gun or torch refer to any mechanismbetween which it and the workpiece the arc is formed). The control atthe torch is dependent on the setting on the control panel. For example,in the preferred embodiment, the control at the torch allows the welderto select between the minimum wire feed speed and the setting on thepanel. Other embodiments allow the control at the torch to adjust thewire feed speed over a range around the wire feed speed set at thepanel. Preferably, both wire feed speed selectors are potentiometers.

[0035] The invention also provides that the run-in speed selection madeon the control panel is dependent upon the wire feed speed set at thepanel (or set by the torch). Specifically, in the preferred embodiment,the run-in speed is selected in a range varying from the minimum speedto the wire feed speed set on the panel or at the torch. Thus, the useris more easily able to control the run-in speed, particularly in itsrelationship to the wire feed speed when welding.

[0036]FIG. 1 shows a block diagram of the preferred embodiment of thepresent invention. A welding power supply or system 100 includes a powersource 104, a controller 102, a wire feeder 106, a torch 110, and a pairof output power lines 111 and 112. A workpiece 114 is also shown. (Powersource, as used herein, refers to the device (often includingtransformers, switches and/or SCRs) that converts line power to weldingpower, such as a Miller Delta Weld®. Source of power, as used herein,refers to a power source, or any other source of power, including theinput connected to the wire feeder on which power is provided.)Generally, these components may be of the type known in the prior art.For example, controller 102 and wire feeder 106 may be similar to orbased on a Miller XRA or XRW® wire feeder (with controller). Powersource 104 may be a Miller Delta. Weld® source of power.

[0037] Controller 102 controls the speed at which wire feeder 106provides wire to torch 110. Controller 102 also controls the operationof power source 104, turning it on and off and, if power source 104 doesnot have its own controller, providing the command signal which dictatesthe output of power source 104.

[0038] Torch 110 is used to activate and deactivate the system bypulling and/or releasing a trigger located thereon. The trigger signalis provided to wire feeder 106, and then to controller 102. Controller102 turns on and off wire feeder 106 and the source of power in responseto the trigger signal. As described thus far, the system is consistentwith those known in the prior art.

[0039] Referring now to FIG. 2, a flow chart showing one implementationof the invention is shown. The flow chart implements the trigger latchaspect of the invention, wherein the trigger latch is not set unless thetrigger is held in the pulled position (or on status) for apredetermined time. The process starts at 201, and at 202 the status ofthe trigger is determined. Status of the trigger is whether not thetrigger is on (or pulled). If the trigger not on the process repeatsdecision 202, until the trigger is on.

[0040] If the trigger is on, the system is activated at step 203.Activation includes turning on at least one of the source of power andwire feeder. In the preferred embodiment the source of power is turnedon by activating a relay or contactor (for example in the wire feeder),and the wire feeder is turned on and will feed wire at the rates set bycontroller 102. In other embodiments only one of the source of power andwire feeder is turned on. Turning on means electronically enabling theoutput, providing a command, isolating the input power, opening aswitch, etc.

[0041] After the system is activated a determination as to whether ornot current is flowing is made at step 204. This step is not part of thepreferred embodiment, but is part of an alternative embodiment. Ifcurrent is not flowing a determination as to whether not the trigger isin the off position is made at step 205. If the trigger is off, then thesystem is deactivated at step 214 and returns to the start. If thetrigger is on then the process returns to step 204 until current beginsto flow.

[0042] When current is detected (using any current detection method) atstep 204 a timer is started at step 206. This timer sets thepredetermined time for which the trigger must be held before the latchis activated. The predetermined time may be set at the factory, maybefixed, or may be adjustable by the user with a potentiometer on thecontrol panel. Thus, predetermined, as used herein, includes adjustableor fixed values.

[0043] After the timer has started the trigger status is againdetermined at step 207. If the trigger is off then the system isde-activated or turned off at step 214, and the process is restarted.This is the path followed when the user is tack welding.

[0044] If the trigger is not off at step 207 then at step 209 it isdetermined whether not the predetermined time has elapsed. If thepredetermined time has not elapsed the process returns to step 207,wherein it continues to check the status of the trigger and then to step209 where it continues to check the status of time elapsed.

[0045] After the predetermined time has elapsed, at step 209, the latchis set at step 210. This is the path taken when using continuouswelding. After the latch is set it is determined if the trigger is offat step. 211. Step 211 is continually repeated until the trigger is off.After the trigger is off the process monitors for a re-trigger at step212. Step 212 is repeated until a re-trigger is sensed. A re-trigger maybe designated as pulling the trigger, or pulling and releasing thetrigger. A re-trigger is used by the welder in the latch mode to turnoff the process. Thus, at step 214 the system is de-activated, andreturns to the start.

[0046] A circuit implementing the trigger-hold is shown in FIG. 3. Anenable/disable switch S1 is connected between pins RC6-2 and RC6-3).When the switch is closed, the trigger hold is disabled. A triggersignal is received on pin RC6-1, and is buffered and filtered through anoptical coupler OC1, a resistor R32, a capacitor C16 and a NAND gate U7(pins 12, 13, 11).

[0047] The trigger signal passes through a NAND gate U7 (pins 5, 6, 4),a NAND gate U7 (pins 1, 2, 3) op amp A4 pins 5, 6 and 7 (havingassociated circuitry resistors R60, R69, and R63), and an RC circuitR64, C33, and a switch Q8 to trigger or start the wirefeeder (and insome embodiments the power source). This circuitry will activate thesystem when the trigger-hold is enabled or disabled.

[0048] The trigger-hold is provided by flip-flop U6, on the NOT-Qoutput. The NOT-Q output is provided to NAND gate U7 pin 2, causing theactivation signal to remain on, even when the trigger is not pulled (asindicated by the output of NAND gate U7 pin 11.

[0049] The latch is controlled by providing the trigger signal (theoutput of NAND gate U7 pin 11) to the clock input of flip-flop U6through circuitry including resistors R36, R50, R58, R59, R45, diode D4,capacitors C37, C42, C21, op amp A4 (pins 12, 13 and 14), NAND gates U8(pins 8, 9, 10) and U8 (pins 12, 13 and 11). An adjustable delay timeris formed by R36, R50, C37, R59, R58, C42 and A4 (pins 13, 12, 14). Thetimer is adjusted by potentiometer R50.

[0050] When the wirefeeder is in not activated, the trigger signal fromU7 pin 11 is low, and flip-flop U6 is reset giving a low output on the Qoutput. The Q output is provided to, and when low turns off a transistorQ4. When the trigger signal coming from U7 pin 11 goes high, thewirefeeder is activated (as described above by U7 (pins 5, 6, 4) and U7(pins 1, 2, 3).

[0051] The signal from U7 pin 11 causes C37 to charge through resistorsR36 and R50. A threshold voltage is created on A4 pin 13 via R59, R58,C42 and the +15 volt supply. When the voltage across C37 exceeds thethreshold on A4 pin 13 the output of A4 pin 14 goes high. This output isfiltered and buffered through R45, C21, U8 (pins 8, 9, 10) U8 (pins 12,13, 11), and then sent to the clock input of U6 which will cause theoutputs Q and not-Q to toggle state if the trigger hold feature isenabled, latching the trigger on. Capacitor C37 is discharged quicklythrough diode D4 and resistor R36 (and Q4 if it is on) after the triggeris released, to allow other trigger transitions to be recognized.

[0052] If the trigger-hold circuit is latched, the wirefeeder willcontinue running as a result of the low signal coming out of U6 pin 12and going into U7 pin 2. Also, U6 pin 13 (the Q output) will be on,turning on transistor Q4 through resistor R37. When the trigger is nowre-pulled, C37 will charge rapidly through resistor R36 and transistorQ4. This causes the output of A4 pin 14 to go high. This output is againbuffered through U8 (pins 8, 9, 10) and U8 (pins 12, 13, 11) and thensent to the clock input of U6 which will cause the outputs Q and not-Qto toggle state, thus removing the trigger-hold latch. The wirefeederwill continue to run as long as the trigger is held pulled.

[0053] When the trigger is finally released, the wirefeeder will beturned off through U7 (pins 5, 6, 4) and U7 (pins 1, 2, 3). Also,capacitor C37 will discharge rapidly through D4 and through R36, whichis small, into U7 pin 11. This completes the trigger-hold cycle andprepares the circuit for the next trigger Thus, the circuitryaccomplishes many of the functions set forth in the flow chart of FIG.2. The latch on, latch off, turn on, and turn off circuits are combinedin a single controller, although they could be isolated in separatecircuits.

[0054] Another aspect of the present invention is having the wire feedspeed selected on the torch be dependent upon, or responsive to, thewire feed speed selected on the control panel. Dependent upon, orresponsive to, means that the torch wire feed speed control is afunction of the control panel wire feed speed control. According to thepreferred embodiment the responsiveness is that the torch wire feedspeed control allows the user to select a wire feed speed anywhere fromthe minimum wire feed speed to the wire feed speed set at the controlpanel. This allows the wire feed speed selector at the torch to have agreater resolution than if it was required to have a range from theminimal wire feed speed to the system maximum wire feed speed. Thegreater resolution allows the user to more easily select the desiredwire feed speed. Alternative embodiments have a different tendency, forexample where the wire feed speed control at the torch is a fixedpercentage more or less than the wire feed speed set at control panel.

[0055] Another aspect of the present invention is that the run-in speedselect on the control panel is similarly dependent upon or responsive tothe control panel wire feed speed. The responsiveness, in the preferredembodiment, is also that the maximum run-in speed is the control panelor torch wire feed speed. This also allows greater resolution of therun-in speed selection. Alternative embodiments allow for a differentdependency, such as a given percentage greater than or less than thecontrol panel wire feed speed.

[0056]FIG. 4 is a diagram of a circuit 400 that implements the torchwire feed speed select and run-in aspects of this invention. Circuit 400includes potentiometers 401, 405 and 409, op amps 402, 406 and 410, anda relay (or electronic switch) 411, 412.

[0057] Potentiometers 401, 405 and 409 allow the user to select variouswire feed speeds. Specifically, potentiometer 401 allows the user to setthe control panel wire feed speed, and is a potentiometer on the controlpanel. The potentiometer setting acts as a voltage divider in aconventional manner, and the divided voltage is buffered by op amp 402.

[0058] The output of op amp 402 is connected to (in electricalcommunication with) or provided to potentiometer 405. Potentiometer 405is the torch wire feed speed selector, and is located on or near thetorch. Potentiometer 405 voltage divides the signal from potentiometer401. As may be seen, the maximum output of potentiometer 405 is theoutput of potentiometer 401.

[0059] The output of potentiometer 405 is provided through a bufferingop amp 406 and a relay 412 to be the welding wire feed speed. Thus,circuit 400 provides a torch wire feed speed selection device responsiveto the control panel wire feed speed.

[0060] Relay 412 and.411 are used to select between a run-in speed and aweld wire feed speed. When relay (or electronic switch) 412 is closed,the welding wire feed speed is provided. When relay (or electronicswitch) 411 is closed the run-in wire feed speed is selected. Relay orswitch 411, 412 is controlled consistent with the prior art, and run-inspeed is selected until the arc is established.

[0061] If the run-in speed is selected it is obtained from the output ofop amp 406 through potentiometer 409. Potentiometer 409 is the run-inpotentiometer on the control panel. Potentiometer 409 voltage divide theoutput of op amp 406, and has as its maximum the output of op amp 406.Thus, circuit 400 provides a run-in speed selection device responsive tothe welding wire feed speed. Thus, it may be seen that the run-in speedis set as a percentage of the wire feed speed during welding. Moreover,potentiometer on the torch is set as a percentage of the wire feed speedon the control panel.

[0062] Numerous modifications may be made to the present invention whichstill fall within the intended scope hereof. Thus, it should be apparentthat there has been provided in accordance with the present invention amethod and apparatus for welding and controlling the activation and wirespeed of a welding system that fully satisfies the objectives andadvantages set forth above. Although the invention has been described inconjunction with specific embodiments thereof, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, it is intended to embrace all suchalternatives, modifications and variations that fall within the spiritand broad scope of the appended claims.

1-45. Cancelled
 46. A method of controlling a welding system comprising:sensing a first signal indicative of a first magnitude of a user-setwelding parameter from a selector located on a control panel of a sourceof power; defining a range of magnitudes about the first magnitude;sensing a second signal indicative of a second magnitude within therange of magnitudes from a remote selector located remotely from thesource of power; and controlling a system output to have the parameterhave the second magnitude.
 47. The method of claim 46 wherein sensingthe second signal includes sensing a second selector located on awelding torch.
 48. The method of claim 46 wherein the range is centeredabout the first magnitude.
 49. A method of controlling a welding systemcomprising; sensing a first user selected magnitude of a weldingparameter from a selector located on a control panel; defining a rangeof magnitudes about the first magnitude; sensing a second signalindicative of a second magnitude within the range of magnitudes from aremote selector located; and controlling the system to operateresponsive to the second user selected magnitude.
 50. A controller for awelding system comprising: means for sensing a first magnitude of a userselected parameter from a selector located on a control panel of asource of power; means for defining a range of magnitudes about thefirst magnitude; means for sensing a second magnitude within the rangeof magnitudes from a remote selector located of a user selectedparameter from a remote selector located remotely from the source ofpower; and means for controlling the system responsive to the firstmagnitude and the second magnitude.
 51. The controller of claim 50wherein the remote selector is located on a welding torch.
 52. A weldingsystem comprising: power means for providing welding power to a weld; afirst selector means for receiving a user selected magnitude for awelding parameter, located on a control panel, and for providing firstoutput indicative of the first magnitude; means for defining a range ofmagnitudes about the first magnitude; a second selector means forreceiving a second user selected magnitude within the range ofmagnitudes for the welding parameter, located remotely from the powermean, and for providing a second output indicative of the secondmagnitude; and a controller means for controlling the system responsiveto the second output.
 53. The apparatus of claim 52 wherein the secondselector means is located on a welding torch.
 54. The apparatus of claim53 wherein the control panel is on the power means.
 55. A weldingsystem, comprising: a first selector, located on a control panel of asource of power, and having a user output indicative of a firstmagnitude of a user-set welding parameter; a second selector, locatedremote from the control panel, and having a second user outputindicative of a second magnitude of the user-set welding parameter,wherein the second magnitude is in a range about the first magnitude; acontroller, connected to and responsive to the second magnitude; and apower supply, connected to and responsive to the controller.
 56. Thesystem of claim 55 wherein the second selector is located on a weldingtorch.
 57. The system of claim 55 wherein the range is centered aboutthe first magnitude.
 58. A controller for a welding system comprising: asensor connected to a selector located on a control panel of a source ofpower, and having a first magnitude output of a user selected parameter;a second-selector, located remote from the control panel, and having asecond user output indicative of a second magnitude of the user-setwelding parameter, wherein the second magnitude is in a range about thefirst magnitude; and an output magnitude controller, responsive to thesecond magnitude.
 59. The controller of claim 58 wherein the remoteselector is located on a welding torch.
 60. A welding system comprising:a power source, disposed to provide welding power to a weld; a firstuser selector, located on a control panel, and providing a first outputindicative of a first magnitude of a welding parameter; a second userselector, located remotely from the power source, and providing a secondoutput indicative of a second magnitude of the welding parameter,wherein the second magnitude is in a range about the first magnitude;and a controller, connected to and responsive to the second magnitude.61. The apparatus of claim 60 wherein the second selector is located ona welding torch.
 62. The apparatus of claim 61 wherein the control panelis on the power source.